Control apparatus for lift bridges



Feb. 12, 1935. w L, x 1,991,336

CONTROL APPARATUS FOR LIFT BRIDGES Filed Aug. 15, 1951 2 Sheets-Sheet 1 INVENTOR. M/fiam Z. 67%

A TTORNE Y.

Feb. 12, 1935.

v w. L. SIX 1,991,336

CONTROL APPARATUS FOR LIFT BRIDGES 2 Sheets-Sheet 2 Filed Aug. 13,- 1931 ATTORNEY.

Patented Feb. 12, 1935 i UNITED *s r rx' r,

v ooN RonArr (19 913136 V a RATUS FOR LIFT- IDGES William L..-Six, Kansas. City, Mo.

Q 7 Application August 13, 1931, Serial No. 556,728 I This invention relates to vertical lift bridges and more particularly to methods of and apparatus for operating and controlling theoperation of a lifting span tomaintain the-.span level and 5 avoid jamming of ends of the span in, guides of supporting towers.

The principal objectsof this invention are to positively actuate apparatus by movements ofga lifting span for controlling and indicating the. operation of the span and to obviate discrepancies in effects of span-operating means resultingjfrom accidental causes such as breakage, or from s1ip'- page of span-supporting cables on sheaves;

Particular objects of this invention are to ren-1 I der means directly responsive to movements of opposite ends of a: lifting span and independent of span-operating machineryfor actuating indie eating and. like safety devices whereby relative movements of'the ends of the span may-be noted and whereby movements of the actuating mechanismfor the lift span may becontrolled to suspend movement of' the lift span when'theflift span gets out of level to prevent jammin of the spanin'the towers. 1

'In accomplishing these and other: objects .of the invention which willbe apparent inthe course of the following description, I haveprovided improved details of structure, the preferred form of the accompanying drawwhich is illustrated in ings, wherein:

Fig. 1 is a diagrammatic elevation of alift bridge having means operative inaocordancev with 7 this inventionfor positively indicating and controlling the movements of opposite ends'of the lifting span.

Fig. 2 is an-enlarged fragmentary vertical'longitudinal sectionv through the upper end portion of one of the lift bridgetowers illustrating .a chain connected with one of the counterweiglits of the lifting span for actuating indicating and control apparatus showndiagrammatically, the housing for a counterweight on the chain being shown fragmentarily and partly broken away.

' Fig. 3 is a fragmentary plan'view of a, tower platform showing a span-supporting sheave and cables, and improved span-operating machinery including a; chain drive; and illustrating the indicating and control-apparatus having no driven relation with the "spaneoperating machinery, the ,view being turned at right angles respectively to theviewsshown in Figs. 1 and 21 i Fig. 4 is a diagrammatic elevationof 'a, tower and adjacent portion of a liftingspam illustrat-' ing a modified'arrangement of the actuatingchain for'the indicating-and control apparatus wherein 8Claims. (01. 116-124)" ratus is notshownin detail.

is not the case.

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it is connected with both the end of the span and thecounterweightfor said end of the span. r Referring more in detail to the drawings:

10, and 12 designate spaced towers supported bypiers 14, and having'platforms 16 provided with journal brackets 18' supporting shafts 20 of sheaves '22.: Sets of cables 'or ropes 24 running in grooves. of the sheaves have opposite ends con nected respectively with counterweights 26 and with opposite ends of a lifting span 28, movable vertically of the towers as in customary practice. The span is normally supported in level position ,by the counterweights, andmay beoperatedvby suitable driving mechanisms on the towers including sets of motors-30 32.

ltflis desirable that the ends of the span move together upwardly and downwardly, and it is necessary to synchronize the movements of opposite ends of the span toavoid jamming of the span in the guides. Various methods and means have been employed heretofore with the inten tion of assuring equal movements of the oppo-- site ends-of a lifting span,-including automati cally synchronizing. span-operating motors and motor-actuated driving means, stopping prime movers when operating unequally, electrically indicating discrepancies in movements of operat-. ing machinery including motors, so that an operator may readjust the machinery to overcome discrepancies in'movements and effects,and the like,.but such synchronizing mechanisms and indicating'or safety appliances have not overcome itliejamming of lift bridges so equipped.

- Conventional forms of control and indicating apparatus include an actuator 46' and actuator shaft48:on each tower having, electrically functioning means associated with suitable circuitsfor respectively operating devices 50 for indicating and controlling the operation of the bridge,

Such control apparatus may'consist of anyof the well known devices. or combinations of devices employed for these purposes in ordinarypractice and well known in'the industry-and since no claim is made to any specific form of apparatus actuated or operated by the shafts 48, the-appa- In present ordinary lift bridge apparatus the shafts 43 :of the actuating devices 46 are geared to 'and'are responsive to'the operating machinery of the lift'span, on the theory that'if the machinery at the'opposite ends of the span operates, synchronously, the ends of the span will move synchronously and the indicating apparatuswill accurately record movements of the span, but,this

In ordinary lift bridge apparatus of the socalled synchronous type the motors transmit their 7 power through trains of gears directly to ring gears on the span-supporting sheaves, depending on friction between the cables and the sheaves to cause movement of the cables and the lifting span.

Under certain conditions there is a slippage of the sheaves under the span-supporting ropes whereby the electrical controls are thrown out of accord because, even though the machineries are operating in synchronism the span is out of level.

In order, therefore, to overcome maladjustment of operating machinery relatively to the span, I

provide positive drive connection between: the machinery and the ends of the lift span and provide for driving the indicating and control apparatus directly by movement of the span so that positive positions of the span are recorded. 7

In the operating machinery included in this invention, the pair of motors 30-32 on each tower have a common shaft 52 provided with a driving gear 54. Reducing gear sets 56 driven by the gear 54 terminate in a driven gear 58 fixed centrally on a shaft 60 'journaledi'n brackets 62-63 supported by the platform. I

Chains 64 and 65 having opposite ends extending respectively through openings in the platform to the counter-weight and over idling pulleys 66 to the adjacent end of the lifting span, engage sprockets 68 and 70 fixed to opposite ends of the Shaft 60. Each assembly or unit of operating machinery at one end of the tower therefore, operates through a pair of chains meshed with the teeth of sprockets to lift the adjacent end of the lifting span or to lift the counterweight to permit the span end to movedownwardly.

The slippage of ropes on the span supporting sheaves will therefore not affect the relative positions of opposite ends of the bridge and synchronous operation of the motors at opposite ends of the bridge will assure synchronousmovements of the ends of the span due to meshed engagement of the gears, chains and sprockets.

With such a positive drive connection the indicating and motor-controlling devices may be connected in the usual manner with the several operating mechanisms with an increased factorof safety due to the elimination of. influence on the controls of slippage of sheaves under the ropes or ropes on the sheaves.

But the hazard of maladjustments of operating mechanisms and jamming of span ends will not be entirely avoided, however, since the breakage of any member of the operating assembly or failure of any member to function normally, may result in the movement of one operating mechanism at a different rate than the other, or in the movement of one end of the bridge a sufficient distance while the other end is stationary to bring about jamming.

To further insure safety and guarantee accurate operation of indicating and control devices,

the actuating means 46 therefor are. operated independently of the main machinery and directly and positively by the movement of the moving load as presently described, the shafts 48 being entirely free from direct influence of the spanoperating elements.

The novel actuating means includes sprockets 72 fixed to the shafts 48, and chains '74 meshed with the teeth of the sprockets and connected with the moving load in any effective manner whereby movements of the opposite ends'of the on the platform.

lift span will directly and positively operate the shafts for actuating the control devices.

One method of rendering a chain responsive to the movements of one end of the lift span is shown in Figs. 1 and 2, wherein one end of the chain is connected with the span counterweight and the opposite end of the chain is provided with a weight '76 slidable in a guide or housing conduit 78 depending from the platform for holding t -e chain taut. Downward movements of the span and counterweightwill then respectively accurately move the shaft 48 rotatatively in opposite directions for actuating the indicating and control devices 50. I

A similar sprocket is mounted on the corresponding control shaft on the opposite tower, and a chain on the sprocket is connected with the counterweight thereof for operating the shaft to actuate indicating and control apparatus 50 associated with the opposite end of the span and oper ating machinery therefor. The two devices will then operate irrespective ,of the relative move ments of the operating'mechanisms whereby the ends of the span are lifted andlowered."

In Fig. 4 an actuator chain 74a is shown havin one end connected with a span counterweightas in Fig. 2, and an opposite end connected with the adjacent end of the lifting span, the chain running over idlers 80- supported by brackets 82 The sprockets and chains responsive to movements of the span endsprovide positive reliable mechanical actuators for the actuator shafts" and may be employed to give dependable measure- .run on the sprockets 72 for actuating-the shafts 48 and provide accurate indications and effective control except in the case of breakage of 'a gear tooth, a chain link or like failure of span-operating mechanisms to function efficiently.

The separate actuator chains are therefore preferred since relatively small strain will be put on the independent chainsand liability of jamming willbe greatly reduced. Not only. may the relations between the ends ofthe span be accurately indicated and operating machinery controlled "in' exact accordance with the movements of the ends of the span, but any failure of the operating machinery to coordinate will be disclosed, and the machinery may be completely controlled to prevent damage that might result to the bridge from lack of synchronous movements of all: or any parts of the operating machinery. a

The improved mechanical control above described, for electrically operated safety devices is applicable to any vertical lift bridge having a single prime mover, or one having separatepower machinery for lifting the two ends of the bridge Whether the separate units are mechanically connected or not. It is especially applicable to vertical lift bridge apparatus wherein the power and machinery for lifting opposite ends of .the bridge comprise mechanically independent units which depend on synchronization for safety of operation. Thedevices operated by the actuators 48 may also be such as to actin any desired manner, for example to cut off power when the bridge is a prescribed amount out. of level due to any cause, for example to failure of operating elements to function correctly. p Y 7 Lift bridge apparatus to which the invention is particularly applicable is generally referred to as the, synchronous motor type of lift, having 1 Patent is:

Cal

- ating the lifting eration of the bridge.

operating mechanism,

. operating mechanism,

. means mounted adjacent each en operating motors transmitting power to racks on counterweight sheaves which may slip under the ropes; Jamming has heretofore been attributed to failure of the'operator to readjust the motor when discrepancies in movements were indicated, or in the case of use of electrical controlling the motors, to failure of the electrical control apparatus.

The use of chain and sprocket drives for operspanobviates errors page of ropes; and the direct response of indicating or control devices to movements of the lifting span insures positive control 'of the operating machinery to bring about accurate and safe op- What I claim and desire to secure by Letters 1. In combination with a lift span including its means for remotely indicating relative movement of v the respective ends of the span, and means directlyactuated by the movement of the ends of the span for operating said indicating means responsive to movements of the" span independent of said operating mechanism whereby relative movements the lift span are indicated.

2. Incombination with a lift span including its indicatingmeans for remotely indicating relative lift. of the respective ends of the span, an actuator for said indicating d ofthe span, and means directly movable by the span for driving the actuators,

3. In a lift bridge including spaced towers, a lift span operable between the towers, and operating means for raising and lowering the lift span relatively to the towers, mechanism for remotely I indicating movement of the respective ends of the lift span comprising actuators located on the respective towers independent of the operating means, sprockets on the actuators, chains connected to the ends of the span and running over said sprockets for operating the actuators, in-

7 said actuators, and

means operably connecting the indicators with the actuators. I

4. In combination with a lift bridge including spaced towers, a lift span operable between the towers, sheaves on weights for counter-balancing the lift span, cables over the sheaves and connected to the counter-balancing weights and to the span, an actuator supported on each tower, a sprocket on each of the actuators, means for. operating said actuators including chains running over said sprockets and connecting the ends of the lift span and the counter-balancing weights independent of said sheaves, and indicators operable by said actuators for indicating relative movements of the respective ends of the spans. I

5. In combination with a lift span and its opmeans connected with the actuating means devices automatically due toslip of the ends of 1 the towers, means including,

erating mechanism including the safety devices for suspending actuation of said operating mechanism, means for actuating the safety devices, and and positively movable with the ends of the lift span whereby the actuating means is operated directly by the movement of the lift span independently of said operating mechanism to suspend actuation of said operating mechanism when the ends of the lift span are out of level a predetermined amount.

6. In a lift bridge including spaced towers, a lift span having ends guidingly mounted relatively to the towers, sheaves 'onthe towers,

counter-balance weights for balancing the lift span, cables operating over the sheaves and have ing their ends connected to the weights and to the ends of the span, operating mechanism on each tower to effect lift of the respective end of the span, and safety devices for controlling said operating mechanismsthe combination of actuatorson the towers, sprockets on the actuators, chains operable over the sprockets and connected to the counter-balance weights whereby the chainsoperate'the actuators upon direct movement of the counter-balance weights regardless of the extent of movement of the sheaves and said operating mechanism, ing the actuators with said safety devices whereby said safety devices are actuated in response to movement of the ends of the span.

'7. In a lift bridge including spaced towers, a

lift span having ends guidingly mounted relatively to the ends of the towers, sheaves 'onthe towers, counter-balance weights for balancing the lift span, cables operating over the sheaves and having their ends connected to the weights and to the ends of the span, operating mechanism on each tower to effect lift of the respective end of the span, and safety devices forcontrolling the operating mechanisms, the combination of actuators mounted on the towers, sprockets on each of the actuators, chains operable over the sprockets and having one end connected to the counter balance weights, weights fixed to the outer end of thechains, guides sup 0r ed by the towers for guiding the weights, and the safety devices are actuated in response to movement of the end of the span;

8. In a lift bridge including its operating mechanism and its moving load including a lift span and its counter-balance weights, and safety devices for suspending operation of'the operating mechanism, the combination of actuators at each erable over the sprockets and connected with the moving load whereby the chains operate the actuators'upon direct movement of the lift span, and means connecting the actuators with the safety devices,

WILLIAM L. SIX.

v means connecting the actuators with said safety devices whereby and means connectf 

